The deployment of voice based emergency notification system (ENS) services, also referred to as REVERSE 911™, is expanding. The use of these systems was demonstrated during the massive California wildfires of 2007 during which voice based emergency notification systems were used to notify homeowners of the need to evacuate.
Emergency notification systems were designed and configured for a static environment in which telephones have a fixed location (e.g., landline phones) and a known number of telephones within an alert area can be calculated. However, many households are replacing fixed landline phones with mobile phones. As a result, an ENS initiator (person or entity initiating calls) may not know which mobile devices are within the specified alert area. Further, subscribers outside of an alert area inadvertently may be notified. Additionally, wireless subscribers that are roaming in an alert area may not be notified of a emergency.